The production of chitosan/xanthan hydrogels is known. U.S. Pat. Nos. 5,620,706 and 5,648,252 describe such hydrogels as inert supports for enzyme immobilisation or for the controlled release of specific antibiotics or anticancer agents. However, the application of such hydrogels as supports, stabilisation and subsequent controlled release of vitamins, amino-acids, nucleic acids and polypeptides has not been proposed yet.
One of the key aspects in the preparation of food additives and dermatological preparations is the preservation of active ingredients prone to degradation, such as vitamins, amino-acids, nucleic acids and polypeptides. Exposure of such ingredients to heat or light accelerates their degradation.
Given the importance of the active ingredients mentioned above, several excipients, such as tablets, capsules, gellules, gels, lotions, ointments, emulsions and simple solutions, have been developed with a view to protect the active ingredients against degradation or simply to render them hydrophobic. However, several drawbacks of these synthetic devices have been identified. In particular their irritation potential and toxicity were put forward.
Due to the inherent limitations of conventional excipients, the use of synthetic polycations was recently proposed. As an example, European patent application # 504 066 A1, 1992, to L'Oréal (France) proposes cosmetic compositions comprising a dispersion of active solid particles coated with a cationic polymer. The aim of the polymeric coating being to increase the stability of the overall composition in addition to preventing degradation of the active ingredient.
Yet an important objective remains unfulfilled. Indeed, there remains an important need to develop new excipients capable of being used in food and dermatological preparations to stabilise thermo- or photo sensitive active ingredients, such as vitamins, nucleic acids, amino-acids and polypeptides.